intermitent electrical pro broblem

[emlclcy]

some time ago I had a problem where the car just wouldn't start, I replaced the dizzy, crank sensor than the ignition coil which fixed things.
she's developed another problem now, cruising at sat 2500rpm the rev counter will drop to zero and the engine cuts out. if I leave her about 5 mins then she runs for another 10 miles or so.
I plugged in the diagnostic lead and it shows cam and crank sensor faults. so I replaced the dizzy and it still has the same problem. do you think I should change the crank sensor? its a real bitch of a job or could it be the ecu?
any ideas welcome
she's a P plate 2ltr petrol B4 estate
cheers
carl